Electric furnace



sept. 1925 H. n... `NASH ELECTRI C FURNACE Filed Oct. 8, 1923 Patented Sept. 1 1925.

HAROLD, L. NASH, 0F SOUTH` NORWALK,

CONNECTICUT, I,aasrciNoa 'ro NASH'ENGI- NEERING COMPANY, or sou'rn NORWALK, coNNnc'rIctrfr, A coaromnoN or CONNECTICUT.

ELECTRIC FURNACE.

Y Application led October 8, 1923. Serial No. 867,806

To all whom it may concern:

Be it known that I, HAROLD L. N AsH, a citizen of the United States, and a resident of South Norwalk, in the county of Fairfield and State of Connecticut, have invented certain new and useful Improvements in Electric Furnaces, of which the following is a specification. K

This invention relates to electric furnaces and particularly to the electric resistance type of furnace in which the crucible is interposed in the electric circuit and its electrical resistance is utilized to generate the heat for the purpose of melting or raising the temperature of metals placed in it. It includes novel means for conveniently supporting and holding the Crucible and attached parts in operative position during heating and for pouring out the contents when suiiiciently heated. It also includes a structural arrangement by which the electrical connections will not be injured by thehigh temperature produced and by which the electric current is most effectively and uniformly distributed. and applied throughout all parts of the Crucible to secure the best heating results. AIt furthermore includes an arrangement of heat insulation by which the loss of heat by radiation or convection is reduced to a minimum. It consists in a` compact device occupying small space and including onlya small number of parts which are of simple construction and easily made and assembled. Its novel and advantageous features will be more fully understood from the following description and claims taken in connection with the accompanying drawing.

In the draw-ing:

Figure 1 is a plan View looking down on a device embodying the invention.

Figure 2 is a vertical section on the line 2--2 of Figure 1.

Figure 3 is a verticalsection through one corner of the lower electric contact member projecting beyond the casing and showing the means for connecting thereto the insulated conducting wire which supplies current, and

Figure 4 is a vertical section corresponding to that of Figure 2, but showing a modified construction at the lower end of the device, including the electric contact member at that end.

Referring first to the device as shown in Figures 1 to 3, the device as a whole is mounted on a suitable supporting stand in such a way that it may be tilted or turned on a pivot. It will be seen by reference to Figures 1 and 2 that the stand shown includes two V-shaped brackets 10 and 11 which are parallel and which have upwardly facing semi-c lindrical bearing sockets 12 and 13 at their upper ends. A supporting casing 14 cylindrical in form and having an open upper. end is provided with integral aligned trunnions or stub shafts 15 and 16, which rotatively fit in the bearing sockets 12 and 13 supporting the device constituting the present invention. An arm 17 is attached to the outer end of stub shaft 16 for convenience in turning or tiltin the device for the purpose of discharging lts contents.

The supporting casing 14 is made of cast iron or other suitable material. A block of carbon, or other material suitable for use as the electric contact member for supplying current to the crucible, acts as a closure for the lower end of the casing 14v extending beyond the margin of the casing 14 at all points and being rectangular in plan view whereby its corners project materially beyond the periphery of the casing 14. This contact member is comparatively thick and of uniform thickness, but there is a slight depression 19 in its upper surface concentrically of the casing 14 having a circular margin, and which depression is adapted to receive and center the lower end of the Crucible 20 which rests upon it. The contact member 183' is secured to the lower end of the casing 14 by means of three equally spaced inwardly projecting integral ears or lugs 21 provided with vertical screw threaded openings, and headed bolts 22 passing through corresponding openings in con- 4 One of these rial, extends materially above the plane of the upper end of the casing 14 and that it is surrounded in casing 14 by suitable insulating material 24. A contact member 26, having substantially the same thickness as contact member 18 and the same rectangular' form in section, is provided with a central cylindrical opening 27 having a diameter slightly greater than the inner diameter of the upper end of the crucible 20; and at the lower edge of this opening or hole there is an annular groove 28 which is angular in cross section and in which the upper end of the crucible lits. This furnishes electrical contact connection between the member 26 and the upper end of the crucible en tirely around its circumference at its upper end, and the crucible supports the Contact member 26 a sutlicient distance above the` upper end of casing 14 to prevent any sparking across that space. The contact member 26 is connected to the casing 14 by headed bolts 29 passing downwardly through openings 30 in said member 26 with a surrounding bushing 31 of insulating material in that Opening, and their lower screw threaded ends enter threaded openings in integral lugs or ears 32, which project a short distance inwardly from the upper edge of casing 14 and, as shown in Figure 1, there are three of these bolts spaced around the casing 14 at regula-r intervals.

A washer 38 formed of insulating material surrounds each bolt 29 and rests on the upper surface of contact member 26 and a metal washer 34 rests on it, and a coiled spring 35 under compression rests at its lower end on washer 34 and at its upper end against the under surface of washer 36. which in turn presses upwardly against' the head of the bolt 29, thus exerting a'yi'elding pressure on the contactl member 26 and through it on the crucible 20. This is to provide for expansion and contraction under varying degrees of temperature which occur during the operation while at the same time maintaining theele'ctric contact of the members 18 and 26 in close engagement with the ends of the crucible at all times.

Electric current is supplied to the upper contact member 26 by means of a self-sustaining insulated conducting wire 37, which is on the arc of a circle and which rests on the projecting corner portions of the con tact member 26, being concentric with the casing 14 and crucible 20. This conducting wire 37 is mechanically and electrically connected to the contact member 26 by means of short flat metahetrips 88, 39, 40 and 41, which strips are of conducting material and have openings through them. Screw threaded bolts 42, 48, 44 and 45 pass vertically through the corner portions of the contact member 26 and through these metal conn tact strips 38, 89, 40 and 41 at a material distance radially from the outer surface of the casing 14. The arrangement of these bolts and contact strips is shown more clearly in Figure 3, which refers specifically to a similar arrangement on the bottom contact member 18. As will be seen by reference to this figure, a headed bolt 46 passes vertically through the contact member 18 and through a washer 47 and through the thin metal contact member 48, which corresponds to the members 88 to 41 above mentioned. A screw threaded nut 49 tightly connect-s the contact 48 to the bolt 46 and the contactmembe'-18.

Referring again to Figures 1 and 2,.the circular conducting wire 37 has secured to it, midway between its ends and on a part which projects a material distancebeyond the edge of the contact member 26, suitable means 50 for detachable electrical connection to a fiexible line wire 51 of an electric circuit which is supplied with current by any suitable generator 52. A similar insulated conducting wire 58 in circular form, conforming in construction and arrangement to the wire 87, rests on the projecting corners of the lower contact member 18 and is mechanically and electrically connected to that Contact member at the four corners by means like that described above and shown in Figure 8. This conducting wire 53 is also provided in midway position and at a material distance outwardly from the margin of the contact member 18 with means 54- for detachably connecting it electrically to the other line wire 55 of the electric circuit supplied by a motor 52.

It will be noted from what has been said above, that the symmetrical form of the contact members and the arrangement of` the electrical connections to them will cause the current passing through the crucible to be distributed throughout it with substantial uniformity at all points, and thus the heating may be uniform and easily and properlv controlled. The connections are furthermore so situated that they are at a material distance from the high heat generated at and by the crucible and thus there is no danger of injury from over heating.

In the modified form of the invention shown in Figure 4, the upper contact member 26 and its means for connection to the casing and its current supply wire 37 are the same in all respects, as in Figure 2, and

vneed no separate description. ln this case,

however, the cylindrical casing 56, corresponding to 14 in the form shown in Figure 2, has greater length vertically than that shown in Figure 2, and its lower end is turned inwardly on a horizontal plane forming a bottom portion 57 with a central cylindrical opening 58 surrounded by a. rib 59. The lower contact member 60 correspond ing to 18 in this form may be said to resemble a short headed bolt having a cylindrical head and stem 61, the head being within the lower end of the casing 56 with the stem portion extending downwardly through the opening 58 and materially beyond the lower end of the casing 56. A washer 62 of insulating material surrounds the stem 61 below the enlarged body portion 60 and supports it, and an insulating sleeve 63 surrounds the stem 61 whereby the member 60 is insulated from the casing 56. The' up r surface of the main body portion 60 liis a slightly depressed central portion 64 on circular lines in which the lower end of the crucible fits and by which it is certered. It will be noted that in this case as well as in the form shown in Figure 2, the contact extends entirely across the lower end of the crucible.

Mounted on and electrically connected to the lower end of .the projecting stem portion of the contact Amember 60 at a material distance below/the casing 56, suitable means 65 is ph sically and electrically connected to it for t e purpose of detachable connection to a line wire 66 of a circuit such as that shown in Figure 2. Although the structure of-the lower contact member in this form shown in Figure 4 is quite different from that in Figure 2, the electric connection is made at one point instead of four equally spaced poi-nts around the periphery, it is nevertheless true that the arts are so arranged that the current passing through the contact members will be distributedthroughout the crucible with substantial uniformity, because of the symmetrical arrangement of the lower Contact member 60 and its stem 61.

In both forms of the invention shown, the upper contact member 26 is provided with a. discharge spout -67' formed in the material of said member extending from the central opening to the outer margin in a lane at right angles to axis of the supporting stub shafts. It is in the form of a groove slightly tapering from the central opening to the outer margin and its bottom surface is on a'convex curve 68 from the lower end of its central opening to a plane near its upper surface at its outer margin. As will be seen by reference to Figures 2 and 4, the bottom surface of said spout at its lower inner end terminates at the surface of the upper end of the crucible at. or slightly outward from, its inner margin whereby any fluid or granular material in the crucible may easily pass outy through it when the crucible is turned on its pivotal support to proper position. The yielding pressure of the contact member 26 Von the upper end of the crucible caused by s )rings 35 will make the joint sufficiently tig it to prevent leakage. The upper contact member may be easily removed to permit the removal of the crucible for cleansing, or for any other purpose, by

vention has many advantages bot i in. struc ture and operation. 1

It constitutes a complete unit, occupying small space and composed of only a few simple structural parts, ready for use at any place desired by simply'connecting the ordinary lines wires of an electric circuit to it.

All of the direct electrical connections be* tween its lparts are what may be called permanent, t us avoiding wear or injury and making them last indefinitely. Aside from the ordinary circuit breaker for turning on and ofi' the circuit, the only electrical connections which it is necessary to make or break in using the device are the two connecting the device in a circuit when a change is made from one circuit to another. This is true even when the parts are so disassembled as to permit the crucible to be removed.

The great convenience of being able to place' the device as a unit in operative position supported by the open top bearing sockets of the stand and when the treatment is finished to discharge the finished product in the crucible by simply operating the handle to turn the device suiiciently.

yThe symmetrical form and arrangemen of the contact members and crucible and of the electrical connections to those members producing uniformi heating of the crucible thus making regulating of the heat easy and producing a uniform product.

The structural arrangement by which the electric contact connections of the line wiresy to the contact members are at such distances from the crucible and metal casing as to prevent them `from being injured byover heating and to prevent any sparking between them and the casing or crucible.

Although two modifications of the invention have been shown for' purposes of illustration, it will be understood that it is not limited to either form specifically beyond what may be indicated in the attached claims. f

Having thus described my invention what I claim as new and desire to secure by Letters Patent is:

1. A resistance electric turnacefcomprising .in combination, an opentop casing, a cruclble in said casing resting on an electric contact member, heat insulating material surrounding said crucible in said casing extending from the lower end of said crucible approximately to a plane near its upper en an electric contact member having a circular opening therethrough of slightly greater diameter than the inner diameter of the upper end of said Crucible concentrivcally resting on and supported by said upper end', means connecting said Contact members to said Casing, and means for connecting said Contact members in an electric circuit.

2. A resistance electric furnace, Comprising in Combination, an open top Casing, a Crucible in said Casing resting on an electric Contact member, heat insulating material surrounding said Crucible in said casing extending lfrom the lower end of said Crucible approximately to a plane near its upper end, an electric Contact -member having a circular opening therethrough of slightly greater diameter than the inner diameter of the upper end of said Crucible concentrically resting on and supported by said upper end, means connecting said Contact members to said casing and meansfor connecting said Contact members in an electric circuit, the said means Connecting the upper Contact member to the Casing being yielding to .permit expansion and contraction under' varying temperatures without breaking.

3. A resistance electric furnace, comprising in Combination, an open top casing, a Crucible in said casing resting on an electric Contact member, heat insulating material surrounding said Crucible in said Casing extending from the lower end of said Crucible approximately tov a plane near its upper end, an electric contact member having a circular opening therethrough of slightly greater diameter than the inner diameter of the upper en'd of said Crucible concentrically resting on and supported by said upper end, means connecting said contact members to said Casing, and means for connecting said Contact members in an electric circuit, the Contact member in which the Crucible rests having a slight depression in its upper surface to receive and center the lower end of said Crucible, and upper Contact member having an annular groove reC- tangular in section in its lower edge around its opening to receive and Center the upper end of said Crucible.

4. A resistance electric furnace, comprising in combination, an open top casing, a Crucible in said casing resting on a flat upper surface of an electric Contact member supported at the lower end of said casing by inwardly projecting portions of said casing, heat insulating material surrounding said Crucible in said casing extending from the lower end of said Crucible approximately to a plane near its upper end, an electric contact member having a circular opening therethrough of slightly greater diameter than the inner diam'eter of the upper end of said Crucible Concentrically resting on and supported by said upper end, means at uniformly spaced distances around l said crucibleand between it and the outer margin of the casing yieldingly connecting said upper contact member to said casing.

5. -A resistance electric furnace, comprising'- in combination, an open top casing,a Crucible in said Casing resting on an electric Contact member.. .heat insulating material surrounding said Crucible in said casing extending from the lower end of said Crucible approximately to a plane near its upper end, anele'citri'c Contact member having a circular 4opening therethrough of slightly greater diameter than the inner diameter of the upper end ofsaid Crucible concentrically resting on and supported 'by said upper end, a plurality of headed bolts extending through bushings of insulating material in vertical openings in said upper Contact member, having screw threaded engagement at their lower ends with inwardly projecting lugs from the upper edge of the Casing with coiled springs under compression surrounding them above said Contact member, bearing at their upper ends against the heads of said bolts and at their lower ends on washers of insulating material for yieldingly connecting said Contact member and casing, and mea-ns for connecting said -contact members in an electric circuit.

6. A resistance electric furnace, com rising in combination, a supporting stan an open top tilting casing pivotally supported by said stand, a Crucible in said casing resting at itslower end in a depression in an electric Contact member, heat and electric insulating material surrounding said crucible in said Casing extendingapproximatcly to a plane near the upper end of said crucible, an electric Contact member having a rabbeted circular opening therein of slightly greater diameter than theJ inner diameter of the upper end of the Crucible resting on and supported by the upper end of the Crucible with its opening concentric therewith, vand means for connecting said Contact members in an electric circuit.

7. A resistance electric furnace, comprising in combination, a supporting stand, an open top tilting casing pivotally supported by said stand, a Crucible in said casing resting at its lower end on an electric Contact member, heat and electric insulating material surrounding said Crucible in said casing extending approximately to a plane near the upper end of said Crucible, an electric Contact member having a Circular opening therein of slightly. greater diameter than the inner diameter of the upper end of the Crucible resting on and supported by the upper end of the Crucible with its hole Concentric therewith, means connecting said parts together, and` means for connecting said Contact members in an electric circuit, the upper Contact member bein provided with a discharge spout in the orm of an outwardly tapering and upwardly curved groove extending from its central opening to its margin in a plane at right angles to that of the pivot. I

8. A resistance electric furnace, comprising in combination, a supporting stand, an open top tilting casing, two short stub shafts projecting in alignment from opposite sides of said casing rotatively supported by upwardly facing semi-cylindrical bearing sockets on said stand, a handle for manual turning secured to the outer end of one. of said stub shafts, a crucible in said casing resting at its lower end on an electric contact member, heat and electric insulating material surrounding said Crucible in said casing extending approximately to-a plane near the upper end of said crucible, an electric contact member having a circular opening therein of slightly greater diameter than the inner diameter of the upper end of the crucible resting on and supported by the upper endet the crucible with its hole concentric ,therewith, and .means for connecting said' contact members in an electric circuit,

9. A resistance electric furnace, comprising in combination, a casing, a Crucible` in said casing, insulating material surrounding said Crucible, electric contact membersenga ing said crucible at its upper and lower en s respectively, one of said contact members projecting a material distance beyond the margin of said crucible and being formed of refractory resistance material, an insulated wire supported by the projecting portion of said member and electrically connected to it at uniformly spaced points around thecrucible, means for Connecting said insulated wire to one Wire of an electric circuit, and means for electrically connecting the other contact member to the other wire of said circuit.

l0. A resistance electric furnace, com rising in combination, a casing, a crucib e in said casing, insulating material surrounding said crucible, an electric contact member closely fitting the lower end of said cruci ble and projecting radially beyond its margin, an electric Contact member closely fitting the up er end of said crucible and projecting ra ially beyond its margin, means for electrically connecting 'the wires of an electric circuit to said contact members respectively, the said contact members being so symmetrically formed and said electric connections to the circuit so symmetrically arranged that the heating current passing through the crucible will be uniformly distributed.

11. A resistance electric furnace, Comprisin in combination, a casing, a crucible in (said casin insulating material surrounding said cruci le, electric contact members engaging said crucible at its upper and lower en s respectively, one of said contact inemtact member to the other Wire of said cry cuit.

12. A resistance electric furnace, com rising in combination, a casing, a crucib e in said casing, insulating material surrounding said crucible, electric contact members enga ing said crucible at its upper and lower en s respectively, both of said contact members being square in outline with their corner portions pro'ecting materially beyond the margin of sai crucible, a. self-sustaining insulated conductin wire for each contact member in circular orm, on a radius much greater than that of the crucible, resting on, secured to and electrically connected to each projecting corner portion of said members respectively, and means for electrically connecting each insulated Wire at a point midway of its length to one Wire of an electric circuit.

13.- Aresistance electric furnace, com rising in combination, a supporting stan an open top tilting casin f pivotall supported by said stand, a crucible in sai casing, an electric Contact member having a central upper surface on which said crucible rests and projecting a material distance outwardly from said casing, an electric contact member having a circular opening therein of slightly greater diameter than the inner diameter of the upper end of said crucible resting on and supported by the upper end of the crucible with lits opening concentric therewith and projecting laterally materially beyond the margin of said crucible, yielding .means connected to said casin pressing said member against the upper en of said crucible, self-sustainin electric conducting members carried by t e projecting portions of said electric contact members and electrically connected to them at material distances from said crucible and container, each of said conducting members being provided with detachable means for connecting it to one of the flexible wires of an electric circuit whereby the device nay be tilted or manually moved.

14. A resistance electric furnace, com rising in combination, a supporting stan an open top tilting casin pivotall supported b said stand, a cruci le in sai casing, an electric contact member having a central upper surface in which said crucible rests an projecting a material distance outllt) wardly from said casing, an electric contact member having a circular opening therein of slightly greater diameter than the inner diameter kof the upper end of said crucible resting on and supported by the upper end of the crucible with its opening concentric therewith and projecting laterally materiall beyond the margin of said crucible, yiel ing means connected to said, casing pressing said member against the upper end of said crucible, self-sustaining electric conducting members carried by the projecting portions of said electric contact members and electrically connected to them at material distances from said crucible and container, each of said conducting members being provided with detachable means for connecting it to one of the flexible wires of an electric circuit whereby the device may be tilted or manually moved, the said electric contact members being of such symmetrical form, and the arrangement of the electrical connections between said contact members and said conducting members being s0 symmetrical that the electric current passing through the crucible will be uniformly distributed. Y

15. A resistance electric furnace, comprising in combination, a supporting stand having bearing sockets with open tops, a casing having stub shafts rotatively mounted in said sockets, a crucible in said casing, insulating material surrounding said crucible below its upper end, contact members in electric engagement with the ends of said crucible and having portions projecting material distances beyond the outer surfaces of said casing, insulated conducting members connected physically and electrically to said projecting portions at material distances from said casing, and means for detachably connecting said conducting members t0 the line wires of an electric circuit.

16. A resistance electric furnace, comprising in combination, a supporting stand having bearing sockets with open tops, a casing having stub shafts rotatively mounted in said sockets, a crucible in said casing, insulating material surrounding said crucible below its upper end, contact members in electric engagement with the ends of said crucible and having portions projecting material distances beyond the outer surfaces of said. casing, insulated conducting members connected physically and electrically to said projecting portions at material distances from said casing, means for detachably connecting said conducting members to the line wires 0f an electric circuit, a discharge spout for said crucible extending from its upper end at right angles to said stub shaft, land a handle for turning said casing and crucible.

17. A resistance electric furnace, compris ing in combination, a supporting stand having bearing sockets with open tops, a casing having stub shafts rotatively mounted in said sockets, a crucible in said casing, insulating material surrounding said crucible below its upper end, contact members in electric engagement with the ends of said crucible and having symmetrical portions projecting material distances beyond the outer surfaces of said casing, insulated conducting members connected physically' and electrically to said projecting portions at material distances from said casing, and means for detachably connecting said conducting members to the line wires of. an electric circuit.

In testimony whereof I hereunto affix my signature.

HAROLD L. NASH. 

